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This roundhouse was reconstructed on the original archaeological foundations of an Iron Age house which was 10 metres in diameter. Like the Old roundhouse, the Earthwatch wall has hazel wattle woven around wooden stakes. The wall has then been covered in daub. The eaves of the roof extend beyond the top of the wall and almost to ground level in order to protect the daubed walls from rain and wind. The angle of the thatched roof is very important it has to be close to 45 degrees in order to shed rain and snow. The rain drips off the reed of the eaves and can, under certain conditions form a drip gully. If grass and weeds are allowed to grow under the low eaves then a drip gully will not form. Fuel for the roundhouse fire would probably have been stored under the eaves. There is no archaeological evidence for supporting posts inside the Earthwatch and we assume that there was a free-spanning roof. A simple jointed tension ring was set on the top of the wall to take the weight of the rafters which each span the distance from the top of the wall to the apex of the roof some 6.5 metres above the central hearth. The rafters were secured to the tension ring by cutting a 'bird beak' joint in the rafter so that they would fit easily over the split oak tension ring. The rafters were secured to each other at the apex of the roof by lashings of hemp twine dipped in tar. River reed was used for the thatch and was secured with twine on to hazel purlins (or batons) which themselves were secured around the rafters. There are no ring beams in the Earthwatch to help deal with the weight of the roof and the heavy winter winds. Because of this, some of the rafters have sagged. To deal with this, we have propped each rafter with an oak post to take the weight. Because there is no evidence for such internal posts we have placed the props on stones which, of course, would not cause any ground disturbance. |
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